The Sunshine to Petrol project is testing a prototype device called the CounterRotating Ring Receiver Reactor Recuperator (called CR5 for short) which turns CO2 into carbon monoxide which could then form part of a liquid fuel.
One way to increase the efficiency of a high-bypass jet engine is to turn the fan into an open rotor, a bit like returning to propellers, but using two rings of stubby counter-rotating blades.